This invention relates to the correction of the human foot disorder of uncompensated forefoot varus, more commonly known as flexible flat foot.
The foot acts as a shock absorber and as a rigid lever for toeing off. In the normal condition when the foot hits the ground, the foot is in pronation when the heel strikes. When the heel strikes the ground, the foot will shiver as it absorbs the shock. The weight bearing then transfers from the heel along the lateral border of the foot until it reaches the fifth metatarsal phalangeal joint or the ball of the foot. Then the weight bearing transfers across the ball of the foot to the great toe.
Because the forefoot of a person with flexible flat foot is uncompensated, (the first metatarsal remains elevated off the ground), the forefoot cannot descend to the ground without excessively pronating the foot. In other words, a person will have to rock their foot to the inside in order to get the great toe down on the ground, and in doing so their foot never achieves the rigid status achieved by a supinated foot or a normal foot.
In the supinated or normal foot, the first metatarsal is always on the ground and the action occurs in the mid-tarsal joint. The mid-tarsal joint rotates slightly and then it locks allowing a person to toe off on the great toe. A person with a pronated foot cannot do this because he cannot put his first metatarsal on the ground unless he rolls his ankle to the inside. This invention allows a person with a flexible flat foot to toe off on the great toe without rolling his ankle to the inside.
The concept of correcting human foot disorders are discussed in patented art and are shown in various devices.
For example, U.S. Pat. No. 2,616,190, Darby, entitled "Walking Angle Corrective Footwear", issued Nov. 4, 1952. This patent shows a device for correction of human foot and leg disorders arising from incorrect weight bearing on the feet. Darby attempts to accomplish this by elevating the medial side of the shoe with an elevated outer fore-sole. Darby would not work for a person who has a flexible flat foot, because with a flexible flat foot, the heel stays in a fairly normal position. The abnormal anatomy occurs at the talus and navicular joint (talo-navicular joint) and in the calcaneus and cuboid joint (calcanco-cuboid joint), which are the two joints which make up the mid-tarsal joint. The difference between the type of problem that Darby is correcting and that which the present invention is correcting is that only the forefoot is in an uncorrected varus state in the flexible flat foot. Therefore, Darby's design does not correct the flexible flat foot because it attempts to correct the heel of the foot which does not need any correcting.
U.S. Pat. No. 4,578,882, Talarico, entitled "Forefoot Compensated Footwear", issued Apr. 1, 1986. This patent shows an angulated wedge-shaped sole sloping upward from the lateral aspect of the forefoot to the medial aspect, reducing excessive pronation and enabling the foot to act as an effective fulcrum and lever for walking or running steps with minimum waste of movement and distortion of the natural foot. If the midfoot is not held in supination, then the foot still tries to evert in the midfoot. Talarico starts his wedge at the base of the fifth metatarsal and angles towards the first metatarsal in a distal fashion. This leaves the midfoot entirely unsupported. In a patient with a normal foot, who can supinate his midfoot, nothing will occur. In the patient with the flexible flat foot, the patient cannot supinate his midfoot properly and the entire arch collapses and the forefoot descends to the surface. If, as in Talarico's model, the forefoot is compensated by a wedge, and the midfoot is not supported, then there will occur a paradoxical motion in which the forefoot is held inverted by the wedge, and the midfoot is allowed to evert. This is exactly what causes the pain in the flexible flat foot, and represents what this device is controlling.
None of the prior art is concerned with the combination of a raised wedge for the forefoot and midfoot, while maintaining the heel in its normal position flat on the ground.
These benefits, together with other objects and advantages of the invention will become more readily apparent to those skilled in the art when the following general statements and descriptions are read in light of the appended drawings.